CN1678720A - Lubricating oil composition for internal combustion engine - Google Patents

Abstract

A lubricating oil composition for an internal combustion engine, which comprises a base oil for a lubricating oil comprising a mineral oil and/or a synthetic oil, (A) 0.001 to 0.5 mass % of an ester of boric acid in terms of boron element and (B) 0.01 to 5 mass % of an ashless antioxidant, both percentages being relative to the total amount of the composition, wherein it contains substantially no metal salt of dithiophosphoric acid and has a sulfur content of 0.2 mass % or less. The lubricating oil composition is extremely excellent in the retention of the base number, the detergency at a high temperature, and the prevention of the cam lifter wear, and also contains substantially no phosphorus and/or sulfur containing anti-wear additive.

Description

Lubricating oil composition for internal combustion engine

technical field

The present invention relates to a lubricating oil composition for an internal combustion engine, and more specifically, to a lubricating oil composition for an internal combustion engine excellent in long-lasting (long drain) performance, high-temperature detergency, and valve system wear prevention.

Background technique

At present, in order to prolong the life of lubricating oil, generally do the following:

(i) Highly refined mineral oil-based base oils as base oils and/or using synthetic oils such as polyalphaolefins and polyol esters;

(ii) A peroxide decomposing agent such as zinc dialkyldithiophosphate (hereinafter referred to as "ZDTP") and a chain terminator such as a phenolic antioxidant are used together as additives. In particular, ZDTP is used as an antioxidant and anti-wear agent as an indispensable additive in current lubricating oils, especially lubricating oils for internal combustion engines.

However, it can be seen that although sulfur-containing compounds such as ZDTP have excellent oxidation resistance, the sulfuric acid released in the process of oxidation or thermal decomposition will accelerate the oxidation and deterioration of lubricating oil, so the life of such lubricating oil is further extended. Extension is limited. In particular, in compositions containing metal-based detergents, ashless dispersants, etc., consumption (deterioration) of total base number, which is an index of acid neutralization characteristics, tends to be accelerated. Therefore, in order to obtain a long-life lubricating oil that is extremely excellent in oxidation stability, it is necessary to thoroughly re-evaluate the formulation of additives, mainly anti-wear agents.

On the other hand, in response to environmental problems in recent years, there is an urgent need to reduce emissions from exhaust gas catalysts such as three-way catalysts, oxidation catalysts, NOx absorption and reduction catalysts, or DPF (diesel particulate filters) installed in internal combustion engines as much as possible. Influenced by gas aftertreatment devices, lubricating oils with low phosphorus, low sulfur or low ash are also desired.

The applicant found that as a lubricating oil that uses less or no ZDTP, a lubricating oil composition formulated with a specific phosphorus-containing anti-wear agent has excellent long-term performance or high-temperature cleaning while maintaining anti-wear properties. properties, low friction, and patents have been applied for their results (for example, Japanese Patent Application No. 2002-015351, Japanese Patent Application No. 2001-315941, etc.). However, there is a limit to low phosphating in order to maintain the same anti-wear performance for preventing valve system wear as when using sulfur-containing compounds such as ZDTP.

On the other hand, for low-phosphorus oil or non-phosphorus oil, research is currently underway, but generally zinc dithiocarbamate is used as an essential component instead of ZDTP to maintain wear resistance (for example, JP-A-62-253691 Publication No. 6-41568, JP-1-500912, JP-63-304095, JP-63-304096, JP-62-243692, JP-62 -501917 bulletin and JP-A-2000-63862 bulletin, etc.). Although the sulfur-containing compounds disclosed in these publications can maintain the wear resistance and oxidation stability to a certain extent like ZDTP as described above, it is difficult to further improve the long-term performance or high-temperature detergency. Therefore, it is desired to develop Produce low-phosphorus, low-sulfur or essentially no phosphorus and sulfur-free engine oils.

Contents of the invention

The present invention has been made in view of the above requirements, and its object is to provide a lubricating oil that has the same anti-friction performance of the valve system as the lubricating oil containing zinc dithiophosphate, and also has long-lasting properties such as oxidation stability and base number maintenance. A lubricating oil composition for an internal combustion engine that is extremely excellent in cleanliness and high-temperature detergency. Another object of the present invention is to provide a lubricating oil composition for an internal combustion engine which is substantially free of phosphorus, low in sulfur, or substantially free of sulfur, and which minimizes the influence on exhaust gas purification treatment devices, especially exhaust gas purification catalysts.

As a result of intensive research, the present inventors have found that a composition containing a boric acid ester and an ashless antioxidant in a specific lubricating oil base oil and not containing a metal dithiophosphate can solve the above-mentioned problems, and thus completed the present invention .

That is, the present invention relates to a lubricating oil composition for an internal combustion engine, which is characterized in that: in lubricating oil base oil composed of mineral oil and/or synthetic oil, based on the total amount of the composition, it contains 0.001 to 0.5% by mass of (A) borate ester and 0.01 to 5% by mass of (B) ashless antioxidant, substantially no metal dithiophosphate, and the sulfur content of the composition is 0.2% by mass or less.

In the aforementioned lubricating oil composition for an internal combustion engine, it is preferable to adjust the total aromatic content of the lubricating base oil to 10% by mass or less, and to adjust the sulfur content to 0.05% by mass or less.

The lubricating oil composition for an internal combustion engine of the present invention preferably contains (C) the metal-based detergent in an amount of 0.005 to 1% by mass in terms of metal elements based on the total amount of the composition.

The metal ratio of the above (C) is preferably 3 or less.

The above-mentioned component (C) is preferably a sulfur-free metal-based detergent.

The lubricating oil composition for an internal combustion engine of the present invention preferably contains the (D) ashless dispersant in an amount of 0.05 to 0.4% by mass in terms of nitrogen element based on the total amount of the composition.

The lubricating oil composition for an internal combustion engine of the present invention preferably contains substantially no phosphorus and has a total sulfur content of 0.05% by mass or less.

The lubricating oil composition for an internal combustion engine of the present invention is preferably used in an internal combustion engine using a sulfur content of 50 mass ppm or less.

Detailed ways

The lubricating oil composition for internal combustion engines of the present invention will be described in detail below.

The lubricating oil base oil in the lubricating oil composition for internal combustion engines of the present invention is not particularly limited, and mineral oil-based base oils and synthetic oil-based base oils used in ordinary lubricating oils can be used.

As mineral oil-based base oils, specifically, desolvation, solvent extraction, hydrocracking, and solvent removal of lubricating oil fractions obtained by vacuum distillation of atmospheric residue obtained from crude oil through atmospheric distillation Base oil obtained by refining one or more of waxes, hydrorefining, etc.; or wax isomerized mineral oil, base manufactured by isomerizing GTL WAX (gas-to-liquid wax) Oil.

Specific examples of synthetic base oils include polybutene or its hydrogenated products; poly-α-olefins such as 1-octene oligomers and 1-decene oligomers or their hydrogenated products; Di(tridecyl) dioate, di-2-ethylhexyl adipate, diisodecyl adipate, di(tridecyl) adipate and di-2-sebacate Diesters such as ethylhexyl ester; polyol esters such as neopentyl glycol ether, trimethylolpropane octanoate, trimethylolpropane nonanoate, 2-ethylpentaerythritol hexanoate and pentaerythritol nonanoate; Aromatic synthetic oils such as alkylnaphthalene, alkylbenzene, and aromatic ester, or their mixtures, etc.

As the lubricating oil base oil of the present invention, the above-mentioned mineral oil-based base oil, the above-mentioned synthetic base oil, or an arbitrary mixture of two or more kinds selected from them can be used. Examples include one or more mineral oil base oils, one or more synthetic base oils, mixed oils of one or more mineral oil base oils and one or more synthetic base oils, and the like.

The lubricating oil base oil of the present invention has no particular limitation on its total aromatic content, but it is preferably adjusted to be 10% by mass or less, more preferably 6% by mass or less, more preferably 3% by mass or less, particularly preferably 2% by mass the following. When the total aromatic content of the lubricating base oil is adjusted to 10% by mass or less, a lubricating oil composition for an internal combustion engine that is more excellent in oxidation stability can be obtained.

The above-mentioned so-called total aromatic content refers to the aromatic fraction (aromatic fraction) content measured according to the ASTM D2549 standard. Usually, in the aromatic fraction, in addition to alkylbenzene and alkylnaphthalene, it also contains anthracene, phenanthrene and their alkylates, compounds with benzene rings fused to four or more rings, or pyridines, quinones, and phenols , naphthyl alcohols and other compounds with heteroaromatic rings.

The sulfur content in the lubricating base oil is not particularly limited, but is preferably adjusted to be 0.05% by mass or less, more preferably 0.01% by mass or less, particularly preferably 0.005% by mass or less. By reducing the sulfur content in the lubricating base oil, it is possible to obtain a low-sulfur lubricating oil composition that is more excellent in long-term performance and can avoid adverse effects on the exhaust gas purification catalyst as much as possible.

The lubricating base oil used in the present invention has no particular limitation on its kinematic viscosity, but its kinematic viscosity at 100°C is preferably 20 mm ² /s or less, more preferably 10 mm ² /s or less. On the other hand, the kinematic viscosity thereof is preferably 1 mm ² /s or higher, more preferably 3 mm ² /s or higher, particularly preferably 4 mm ² /s or higher. When the kinematic viscosity of the lubricating base oil at 100°C exceeds 20 mm ² /s, its low-temperature viscosity characteristics deteriorate. On the other hand, when the kinematic viscosity is less than 1 mm ² /s, due to the formation of The oil film of the lubricant is not sufficient, so the lubricating performance is poor, and the evaporation loss of the lubricating base oil is increased, so this is not advisable.

The evaporation loss of the lubricating base oil is not particularly limited, but is preferably 20% by mass or less, more preferably 16% by mass or less, particularly preferably 10% by mass or less in terms of NOACK evaporation. When the evaporation amount of the lubricating base oil exceeds 20% by mass, not only the evaporation loss of the lubricating oil increases, but also sulfur compounds and metal components in the composition accumulate together with the lubricating base oil in the exhaust gas purification device It may have adverse effects on exhaust gas purification performance, so it is not advisable. The NOACK evaporation mentioned here refers to the CEC L-40-T-87 standard, at 250°C, a 60g lubricating oil sample is kept under reduced pressure from normal pressure to 20×9.80665Pa (20mmH ₂ O) Evaporation measured after 1 hour.

The viscosity index of the lubricating base oil is not particularly limited, but it is preferably 80 or more, more preferably 100 or more, and more preferably 120 or more in order to obtain excellent viscosity characteristics from low temperature to high temperature. When the viscosity index is less than 80, the low-temperature viscosity characteristics deteriorate, which is not preferable.

The component (A) in the lubricating oil composition for an internal combustion engine of the present invention is a boric acid ester. This boric acid ester is usually used simultaneously as a bearing anticorrosion agent and a compound containing sulfur and/or phosphorus (such as JP-A-63-304095, JP-63-304096, JP-2000-63865 and JP- KOKAI Publication No. 2000-63871), but more recently compounds having an effect of increasing the friction coefficient between metals can be cited (Japanese Patent Application Publication No. 2002-226882).

Examples of the boric acid ester in the present invention include compounds represented by the following general formula (1) or (2), derivatives thereof, and the like.

In general formulas (1) and (2), R ¹ to R ⁶ each represent a hydrocarbon group having 1 to 30 carbon atoms, and they may be the same or different.

Specific examples of hydrocarbon groups having 1 to 30 carbon atoms include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, and undecyl. Alkyl groups with 1 to 30 carbon atoms such as dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl and octadecyl (these alkane The group can be linear or branched); vinyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, Alkenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, octadecenyl and other alkenyl groups with 2 to 30 carbon atoms (alkenyl The group can be a straight chain or a branched chain, and the position of the double bond is arbitrary); cyclopentyl, cyclohexyl and cycloheptyl and other cycloalkyl groups with 5 to 7 carbon atoms; methylcyclopentyl base, dimethylcyclopentyl, methylethylcyclopentyl, diethylcyclopentyl, methylcyclohexyl, dimethylcyclohexyl, methylethylcyclohexyl, diethylcyclohexyl, methyl Cycloheptyl, dimethylcycloheptyl, methylethylcycloheptyl, diethylcycloheptyl and other alkylcycloalkyl groups with 6 to 11 carbon atoms (the substitution position of the alkyl group on the cycloalkyl group is arbitrary); phenyl, naphthyl and other aryl groups with 6 to 18 carbon atoms; tolyl, xylyl, ethylphenyl, propylphenyl, butylphenyl, pentylphenyl, hexylphenyl phenyl, heptylphenyl, octylphenyl, nonylphenyl, decylphenyl, undecylphenyl, dodecylphenyl, diethylphenyl, dibutylphenyl and dioctylphenyl Alkylaryl groups with 7 to 26 carbon atoms, such as phenyl, etc. (the alkyl group can be straight chain or branched, and the substitution position on the alkyl group is arbitrary); benzyl, phenylethyl C7-12 aralkyl groups such as phenylpropyl group, phenylbutyl group, phenylpentyl group, phenylhexyl group (the alkyl group may be linear or branched) and the like.

The above-mentioned hydrocarbon group with 1 to 30 carbon atoms is preferably a hydrocarbon group with 2 to 24 carbon atoms, more preferably a hydrocarbon group with 3 to 20 carbon atoms, more specifically, preferably a hydrocarbon group with 1 to 30 carbon atoms An alkyl group or an aryl group having 6 to 24 carbon atoms, more preferably an alkyl group having 3 to 18 carbon atoms, more preferably an alkyl group having 4 to 12 carbon atoms.

The boric acid ester represented by the general formula (1) is usually obtained by reacting 1 mol of orthoboric acid (H ₃ BO ₃ ) with 3 mol of the alcohol having 1 to 30 carbon atoms.

The boric acid ester represented by the general formula (2) is usually obtained by reacting 1 mol of orthoboric acid (H ₃ BO ₃ ) with 1 mol of the alcohol having 1 to 30 carbon atoms.

The conditions of these reactions are not particularly limited, but they are usually carried out at 100° C. or higher, so that the generated water is removed at the same time, so it is particularly preferable.

As the derivative of component (A), for example, among the organic borates described in JP-A-2002-226882, compounds that do not contain phosphorus or sulfur, for example, organic borate-poly Amine condensates (polyamine condensates of the above-mentioned borate esters), organic borate-polyol condensates (polyol condensates of the above-mentioned borate esters), and the like. Preferable examples of component (A) include: triethyl borate, tri-n-propyl borate, triisopropyl borate, tri-n-butyl borate, tri-sec-butyl borate, tri-tert-butyl borate ester, trihexyl borate, trioctyl borate, tridecyl borate, tridodecyl borate, trihexadecyl borate, trioctadecyl borate, triphenyl borate Esters, tribenzyl borate, triphenylethyl borate, tricresyl borate, triethylphenyl borate, tripropylphenyl borate, tributylphenyl borate and trinonyl borate, etc. Among them, tri-n-butyl borate, trioctyl borate, tridecyl borate and the like are particularly preferable.

In the lubricating oil composition for internal combustion engines of the present invention, the lower limit of the content of the component (A) is 0.001% by mass or more in terms of boron element based on the total amount of the composition in order to exhibit anti-wear properties. , preferably at least 0.01% by mass, particularly preferably at least 0.04% by mass. The upper limit of the component (A) content is usually 0.5% by mass or less, preferably 0.2% by mass or less, more preferably 0.1% by mass or less, based on the total amount of the composition in terms of boron conversion. When the content of the component (A) exceeds the above-mentioned upper limit, it is difficult to obtain an anti-wear effect corresponding to the content, which is not preferable.

Component (B) in the lubricating oil composition for internal combustion engines of the present invention is an ashless antioxidant, and any antioxidant commonly used in lubricating oils, such as phenolic antioxidants and amine antioxidants, can be used.

Examples of phenolic antioxidants include 4,4'-methylenebis(2,6-di-tert-butylphenol), 4,4'-bis(2,6-di-tert-butylphenol) , 4,4'-bis(2-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 2,2'-methylene Methylbis(4-methyl-6-tert-butylphenol), 4,4'-butylenebis(3-methyl-6-tert-butylphenol), 4,4'-isopropylidenebis( 2,6-di-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-nonylphenol), 2,2'-isobutylenebis(4,6-dimethyl phenylphenol), 2,2'-methylene bis(4-methyl-6-cyclohexylphenol), 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl- 4-ethylphenol, 2,4-dimethyl-6-tert-butylphenol, 2,6-di-tert-α-dimethylamino-p-cresol, 2,6-di-tert-butyl- 4(N,N'-dimethylaminomethylphenol), 4,4'-thiobis(2-methyl-6-tert-butylphenol), 4,4'-thiobis(3-methylphenol) base-6-tert-butylphenol), 2,2'-thiobis(4-methyl-6-tert-butylphenol), bis(3-methyl-4-hydroxy-5-tert-butylbenzyl ) sulfide, bis(3,5-di-tert-butyl-4-hydroxybenzyl) sulfide, 2,2'-thiodiethylenebis[3-(3,5-di-tert-butyl-4 -hydroxyphenyl)propionate], tridecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, pentaerythritol tetrakis[3-(3,5-di-tert Butyl-4-hydroxyphenyl) propionate], octyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, octadecyl-3-(3,5 - Di-tert-butyl-4-hydroxyphenyl) propionate, octyl-3-(3-methyl-5-tert-butyl-4-hydroxyphenyl) propionate, etc. 3-methyl-5- Preferable examples are fatty acid esters substituted with t-butyl-4-hydroxyphenyl. These may also be used in combination of two or more. Of these, sulfur-free compounds are particularly preferred.

Examples of the amine antioxidant include phenyl-α-naphthylamine, alkylphenyl-α-naphthylamine, and dialkyldiphenylamine. These may be used in combination of two or more.

The above-mentioned phenolic antioxidants and amine antioxidants may also be used in combination.

When the component (B) is contained in the lubricating oil composition for internal combustion engines of the present invention, its content is usually 5% by mass or less, preferably 3% by mass or less, more preferably 2.5% by mass, based on the total amount of the composition. Mass% or less. When the content exceeds 5% by mass, sufficient oxidation resistance corresponding to the compounding amount cannot be obtained. On the other hand, the lower limit of the content is 0.01% by mass or more, preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, based on the total amount of the composition in order to obtain sufficient oxidation resistance.

The lubricating oil composition for an internal combustion engine of the present invention does not substantially contain metal dithiophosphate. As dithiophosphate metal salts, starting from zinc dithiophosphate, dithiophosphoric acid with various metals such as Group I metals, Group II metals, aluminum, lead, tin, manganese, cobalt, Salt formed by nickel and copper. The term "substantially not containing metal dithiophosphate" means that when they are used alone, they contain 0.05% by mass of the component (A ) composition, the amount that cannot fully exert the anti-wear performance of the valve system and does not significantly impair the effect of the present invention, for example, based on the total amount of the composition, is 0.04 mass in terms of phosphorus conversion % or less, preferably 0.01 mass % or less, particularly preferably 0.001 mass % or less, but essentially they are intentionally not contained at all.

The lubricating oil composition for an internal combustion engine of the present invention, when having the above composition, can be a composition excellent in anti-wear performance of the valve system and extremely excellent in oxidation stability, but when it further contains (C) a metal-based detergent, (D) When used as an ashless dispersant, the oxidation stability can be further improved, and a composition with excellent alkali value maintenance and high-temperature detergency can be obtained.

As the component (C) in the lubricating oil composition for internal combustion engines of the present invention, any compound used as a metal-based detergent for lubricating oil can be used, but specifically, for example, compounds selected from alkali metals and alkaline earths can be used. Metal-based detergents of one or more of metal sulfonates, alkali metal or alkaline earth metal phenates, alkali metal or alkaline earth metal salicylates, alkali metal or alkaline earth metal carboxylates, etc. Among them, sulfur-free alkali metal or alkaline earth metal phenates, alkali metal or alkaline earth metal salicylates or alkali metal or alkaline earth metal carboxylates are preferably used as essential ingredients, especially when using alkali metal or alkaline earth metal When the acid salt is used, it is particularly preferable in terms of obtaining a low-sulfur or substantially sulfur-free lubricating oil composition excellent in oxidation stability, base number maintenance, and high-temperature detergency.

The so-called alkali metal or alkaline earth metal sulfonates are alkali metal or alkaline earth metal salts of alkylaromatic sulfonic acids obtained by sulfonating alkylaromatic compounds with a molecular weight of 1300 to 1500, preferably 400 to 700, especially are magnesium and/or calcium salts, preferably calcium salts are used.

Specific examples of the above-mentioned alkylaromatic sulfonic acid include so-called petroleum sulfonic acid and synthetic sulfonic acid. As the petroleum sulfonic acid mentioned here, the product obtained by sulfonating the alkylaromatic compound in the lubricating oil fraction of mineral oil or the so-called petroleum by-produced in the production of white oil (fluid paraffin) are generally used. Sulfonic acid etc. On the other hand, as the synthetic sulfonic acid, for example, a product having a linear or branched shape obtained by alkylating benzene with a polyolefin as a by-product from a factory producing alkylbenzene as a raw material for detergents can be used. A product obtained by sulfonating an alkylbenzene with a chain alkyl group, or a product obtained by sulfonating an alkylnaphthalene such as dinonylnaphthalene, or the like. In addition, fuming sulfuric acid or anhydrous sulfuric acid is generally used as a sulfonating agent for sulfonating these alkylaromatic compounds.

As the alkali metal or alkaline earth metal phenate, straight chain or branched chain alkyl (they are primary alkyl, secondary alkyl, tertiary alkyl) having 4 to 30 carbon atoms, preferably 6 to 18, can be mentioned. are all possible), alkali metal or alkaline earth metal salts, especially magnesium and/or calcium salts, of alkylphenols, alkylphenol sulfides, Mannich reactants of alkylphenols. Of these, sulfur-free alkali metal or alkaline earth metal phenates are particularly preferred.

As alkali metal or alkaline earth metal salicylate, there can be mentioned alkali metal or alkaline earth metal salts of salicylic acid having 1 or 2 hydrocarbon groups with 1 to 40 carbon atoms, especially magnesium salt or calcium salt . Examples thereof include compounds represented by the following general formula (3).

In the general formula (3), R ¹¹ represents a hydrocarbon group with 1 to 40 carbon atoms, preferably 1 to 30, preferably an alkyl group, M represents an alkaline earth metal, preferably calcium or magnesium, particularly preferably calcium, and n is 1 or 2.

As the above-mentioned ^R11 , specifically, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, Tridecyl, Tetradecyl, Pentadecyl, Hexadecyl, Heptadecyl, Octadecyl, Nonadecyl, Eicosyl, Icodecyl, Docosane Tricosyl group, tetracosyl group, pentadecyl group, hexadecyl group, heptacyl group, octadecyl group, nonacosyl group, triaconyl group, etc., They may be straight-chain or branched and they may also be primary, secondary or tertiary.

As alkali metal or alkaline earth metal sulfonates, alkali metal or alkaline earth metal phenates, alkali metal or alkaline earth metal salicylates, etc., not only the above-mentioned alkylaromatic sulfonic acids, alkylphenols, alkylphenols Sulfides, Mannich reactants of alkylphenols, alkyl salicylic acids, etc. react directly with alkaline earth metal bases such as magnesium and/or calcium alkaline earth metal oxides or hydroxides, or with alkalis such as sodium or potassium salts Neutral salts obtained by reaction of metal salts followed by displacement with alkaline earth metal salts, but also by heating such neutral salts with an excess of alkaline earth metals or alkaline earth metal salts or alkaline earth metals or alkaline earth metal bases in the presence of water or the overbased salt obtained by reacting the neutral salt with an alkaline earth metal base in the presence of carbon dioxide or boric acid or borate.

The above-mentioned neutral salts, basic salts, overbased salts, mixtures thereof, and the like can be used as the metal-based detergents referred to in the present invention.

Metal-based detergents are usually sold in a state diluted with a light lubricating base oil, and are available, but it is generally desirable to use a metal content of 1.0 to 20% by mass, preferably 2.0 to 16% by mass. product.

In the present invention, the total base number of the component (C) is usually 0 to 500 mgKOH/g, preferably 20 to 450 mgKOH/g, and one or two or more selected from these may be used together. The total base number mentioned here refers to the total base number based on the potentiometric titration method (base number-perchloric acid method) measured in accordance with the 7. standard of JIS K 2501 "Petroleum products and lubricating oil-neutralization value test method". base value.

As the component (C) of the present invention, there is no particular limitation on its metal ratio. Generally, one or more metal-based detergents with a metal ratio of 20 or less can be used in combination. However, it is preferable to use a metal ratio of 3. Below, more preferably 1.5 or less, particularly preferably 1.2 or less, metal-based detergents are particularly preferred because they are more excellent in oxidation stability, base number maintenance, and high-temperature detergency. The metal ratio mentioned here refers to a value expressed by the valence of the metal element in the metal-based detergent × the content of the metal element (mol%)/the content of the soap group (mol%), and the so-called metal element refers to calcium , magnesium, etc., the so-called soap group refers to sulfonic acid group, salicylic acid group and the like.

In the present invention, the content of component (C) is usually 1% by mass or less, preferably 0.5% by mass or less, and more preferably 0.4% by mass or less in terms of metal element conversion. It is further reduced to 1.0% by mass or less, preferably 0.3% by mass or less. In addition, the content of component (C) is 0.005% by mass or more, preferably 0.01% by mass or more, more preferably 0.05% by mass or more, especially 0.2% in order to improve oxidation stability, base number maintenance, and high-temperature detergency. Mass % or more can obtain the composition which can maintain the base number and high-temperature detergency for a longer period of time, so it is especially preferable. The sulfated ash content mentioned here refers to the value measured according to the method specified in JIS K 2272, 5. "Test method for sulfated ash content", and is mainly derived from additives containing metals.

As the (D) ashless dispersant, any ashless dispersant used in lubricating oil can be used, for example, one having at least one linear or branched one having 40 to 400 carbon atoms in the molecule Alkyl or alkenyl nitrogen-containing compounds or their derivatives, or modified alkenyl succinimide, etc. One kind or two or more kinds selected from them may be blended.

The number of carbon atoms in the alkyl or alkenyl group is 40-400, preferably 60-350. In the case where the number of carbon atoms in the alkyl or alkenyl group is less than 40, the solubility of the compound relative to the lubricating base oil is too low, and when the number of carbon atoms in the alkyl or alkenyl group exceeds 400, due to the lubrication of the internal combustion engine It is also undesirable that the low-temperature fluidity of the oil composition deteriorates. These alkyl or alkenyl groups may be linear or branched, but specific examples include oligomers of olefins such as propylene, 1-butene, and isobutylene, or ethylene A branched alkyl group or a branched alkenyl group derived from a co-oligomer of propylene, etc.

As a specific example of a component (D), the following compounds are mentioned, for example. One or two or more compounds selected from among them may be used.

(D-1) Succinimide or its derivatives having at least one alkyl or alkenyl group with 40 to 400 carbon atoms in the molecule;

(D-2) There is at least one alkyl or alkenyl benzylamine or its derivatives with 40 to 400 carbon atoms in the molecule;

(D-3) A polyamine or a derivative thereof having at least one alkyl or alkenyl group having 40 to 400 carbon atoms in a molecule.

As the succinimide of the above-mentioned (D-1), more specifically, compounds represented by the following general formula (4) and general formula (5), etc. may be mentioned.

In the general formula (4), R ²⁰ represents an alkyl or alkenyl group having 40-400 carbon atoms, preferably 60-350, and h represents an integer of 1-5, preferably 2-4.

In the general formula (5), R ²¹ and R ²² respectively represent an alkyl or alkenyl group with 40 to 400 carbon atoms, preferably 60 to 350, preferably polybutenyl, and i represents 0 to 4, preferably An integer of 1 to 3.

Succinimide includes so-called monotype succinimide represented by general formula (4) in which succinic anhydride is added to one end of a polyamine and general formula (5) in which succinic anhydride is added to both ends of a polyamine. ) represents the so-called double-type succinimide, but in the composition of the present invention, any one of them or a mixture thereof may be contained.

As a method for producing these succinimides, a compound having, for example, an alkyl or alkenyl group having 40 to 400 carbon atoms, such as a poly(iso) Butene and maleic anhydride are reacted at 100-200°C to obtain polybutenyl succinic acid, which is then reacted with polyamines. Specific examples of the polyamine include diethylenetriamine. Triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, etc.

As said (D-2) benzylamine, the compound represented by following general formula (6) is mentioned more specifically.

In the general formula (6), ^R23 represents an alkyl or alkenyl group having 40-400 carbon atoms, preferably 60-350, and j represents an integer of 1-5, preferably 2-4.

As the preparation method of this benzylamine, after polyolefins such as propylene oligomer, polybutene and ethylene-α-olefin copolymer are reacted with phenol to obtain alkylphenol, formaldehyde and polyamine ( For example, diethylenetriamine, tetraethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, etc.) are obtained by Mannich reaction.

As said (D-3) polyamine, the compound represented by following general formula (7) is mentioned more specifically.

R ²⁴ -NH-(CH ₂ CH ₂ NH) _k -H (7)

In the general formula (7), ^R24 represents an alkyl or alkenyl group having 40-400 carbon atoms, preferably 60-350, and k represents an integer of 1-5, preferably 2-4.

As the preparation method of the polyamine, after polyolefins such as propylene oligomers, polybutene and ethylene-α-olefin copolymers are chlorinated, they are mixed with polyamines (such as ammonia or ethylenediamine) , diethylenetriamine, tetraethylenetetramine, tetraethylenepentamine and pentaethylenehexamine, etc.) obtained by reaction.

In addition, the nitrogen-containing compound derivatives mentioned as an example of the component (D) include, for example, the above-mentioned nitrogen-containing compound and a monocarboxylic acid (fatty acid, etc.) having 1 to 30 carbon atoms or Oxalic acid, phthalic acid, trimellitic acid, pyromellitic acid and other polycarboxylic acids with 2 to 30 carbon atoms, hydroxyl (poly) alkylene carbonate, etc., neutralize part or all of the remaining amino groups and / or imino group, the so-called acid-modified compound obtained after amidation; the so-called Boron modified compound; the so-called phosphoric acid modified compound obtained by making the aforementioned nitrogen-containing compound react with phosphoric acid to neutralize part or all of the remaining amino and/or imino groups and perform amidation; make the aforementioned nitrogen-containing compound react with sulfur A sulfur-modified compound obtained by the action of a compound; and a modified compound obtained by combining the aforementioned nitrogen-containing compound with two or more modified compounds selected from acid modification, boron modification, phosphoric acid modification, and sulfur modification. sexual compounds, etc. Among these derivatives, boron-modified compounds of polybutenyl succinimide are excellent in heat resistance, oxidation resistance, and wear resistance. In the lubricating oil composition for internal combustion engines of the present invention, since the alkali Value maintenance, high temperature detergency and wear resistance, so it is effective.

When the component (D) is contained in the lubricating oil composition for internal combustion engines of the present invention, its content is usually 0.01% by mass or more, preferably 0.05% by mass, in terms of nitrogen element conversion based on the total amount of the composition % or more, more preferably 0.07 mass % or more, usually 0.4 mass % or less, preferably 0.2 mass % or less, particularly preferably 0.16 mass % or less. When the content of component (D) is less than 0.01% by mass in terms of nitrogen element, the effect of further improving the high-temperature detergency is not large, and when it exceeds 0.4% by mass, the low-temperature detergency of the lubricating oil composition for internal combustion engines A substantial deterioration in liquidity is not advisable.

In order to further improve the performance of the lubricating oil composition for internal combustion engines of the present invention, various additives generally used in lubricating oils may be added according to different purposes. Such additives include, for example, antiwear agents other than component (A), friction modifiers, viscosity index improvers, corrosion inhibitors, rust inhibitors, demulsifiers, metal deactivators, defoamers, and Additives such as colorants, etc.

Examples of antiwear agents other than component (A) include zinc dithiocarbamates, disulfides, sulfurized olefins, sulfurized oils, sulfurized esters, thiocarbonates, thioamino Sulfur-containing anti-wear agents such as formates; phosphorus-containing anti-wear agents such as phosphites, phosphates, phosphonates and their amine salts or metal salts; thiophosphites, thiophosphates, Thiophosphonates and their amine salts or metal salts and other sulfur and phosphorus antiwear agents. Among them, the sulfur-containing anti-wear agent can be adjusted with lubricating base oil or other sulfur-containing additives, as long as the sulfur component contained in the composition does not exceed the limit of 0.2% by mass, but it is more preferable not to contain it. Among them, the phosphorus-containing anti-wear agent can be calculated in terms of phosphorus element, within the range that does not significantly poison and deteriorate the exhaust gas purification catalyst, for example, 0.04% by mass or less, preferably 0.01% by mass or less, However, it is more preferable not to contain it.

As the friction modifier, any compound generally used as a lubricant oil friction modifier can be used, for example: molybdenum dithiocarbamate, molybdenum amine complexes, molybdenum-succinimide complexes, etc. Molybdenum-based friction modifiers; and amine compounds having at least one alkyl or alkenyl group with 6 to 30 carbon atoms in the molecule, especially a straight-chain alkyl or straight-chain alkenyl group with 6 to 30 carbon atoms, Ashless friction modifiers such as fatty acid esters, fatty amides, fatty acids, fatty alcohols, and aliphatic ethers can usually be contained in the range of 0.1 to 5% by mass, but when molybdenum dithiocarbamate is contained, it is preferably The amount of base oil and other additives used together is adjusted so that the sulfur content of the composition is 0.2% by mass or less, preferably 0.1% by mass or less, particularly preferably 0.05% by mass or less. Among these, it is particularly preferable to use an ashless friction modifier because it does not contain sulfur or metal.

As the viscosity index improver, specifically, polymers or copolymers of one or two or more monomers selected from various methacrylates, or their hydrogenated products, such as so-called non-dispersed type viscosity index improver, or the so-called dispersion type viscosity index improver which copolymerizes various methacrylates containing nitrogen compounds, non-dispersion type or dispersion type ethylene-α-olefin copolymer (as α-olefin For example, propylene, 1-butene, 1-pentene) or its hydrogenated product, polyisobutylene or its hydrogenated product, styrene-diene copolymer hydrogenated product, styrene-anhydrous Maleate copolymer and polyalkylstyrene, etc.

The molecular weights of these viscosity index improvers need to be selected in consideration of shear stability. Specifically, the number-average molecular weight of the viscosity index improver, for example, in the case of dispersed and non-dispersed polymethacrylates, is usually 5,000 to 1,000,000, preferably 100,000 to 900,000, but polyisobutylene or its additives In the case of a hydrogen product, it is usually 800 to 5,000, preferably 1,000 to 4,000, and in the case of an ethylene-α-olefin copolymer or its hydrogenated product, it is usually 800 to 500,000, preferably 3,000 to 200,000.

Among such viscosity index improvers, when an ethylene-α-olefin copolymer or a hydrogenated product thereof is used, a composition having particularly excellent shear stability can be obtained. Any one or two or more compounds selected from the aforementioned viscosity index improvers may be contained in an arbitrary amount. The content of the viscosity index improver is usually based on the composition, preferably 0.1 to 20% by mass.

Examples of preservatives include benzotriazole-based, tolyltriazole-based, thiadiazole-based, and imidazole-based compounds.

Examples of rust inhibitors include petroleum sulfonates, alkylbenzenesulfonates, dinonylnaphthalenesulfonates, alkenyl succinates, and polyol esters.

Examples of the demulsifier include polyalkylene glycol-based nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, and polyoxyethylene alkylnaphthalene ether.

As metal deactivators, for example, imidazoline, pyrimidine derivatives, alkylthiadiazole, mercaptobenzothiazole, benzotriazole or its derivatives, 1,3,4-thiadiazole polysulfide , 1,3,4-thiadiazolyl-2,5-bisdialkyldithiocarbamate, 2-(alkyldithio)benzimidazole and β-(o-carboxybenzyl Thio)propionitrile, etc.

Examples of the antifoaming agent include silicone, fluorosilicone, and fluorine-containing alkyl ether.

When these additives are contained in the lubricating oil composition for internal combustion engines of the present invention, the content thereof is preferably within the following range, that is, based on the total amount of the composition, the anticorrosion agent, rust inhibitor, and demulsifier are respectively 0.005 to 5% by mass, 0.005 to 1% by mass of the metal deactivator, and 0.0005 to 1% by mass of the defoamer.

The lubricating oil composition for an internal combustion engine of the present invention is a low-sulfur lubricating oil composition for an internal combustion engine that does not substantially contain the metal dithiophosphate as described above and has a sulfur content of 0.2% by mass or less. The abrasion agent may be a composition substantially free of phosphorus. By selecting the lubricating oil base oil and various additives, it is also possible to obtain a low-sulfur internal combustion engine lubricating oil composition in which the total sulfur content of the composition is preferably 0.1% by mass or less, more preferably 0.05% by mass or less, particularly preferably 0.01% by mass or less thing. In particular, if attention is paid to the sulfur content of the mineral oil fraction as a diluent contained in the lubricating oil base oil and various additives, a lubricating oil for internal combustion engines with a sulfur content of 0.001% by mass or less or substantially no sulfur can be obtained combination.

In the lubricating oil composition for internal combustion engines of the present invention, the antiwear agent does not contain metal, and compared with the case of using a metal-containing antiwear agent, for example, ZDTP, it is possible to reduce the amount of sulfuric acid ash derived from metal in the composition (without undesired Equivalent to metallic boron). Then, through the selection of additives containing other metals, etc., the sulfated ash content derived from the metal in the composition can be reduced to preferably 1.0% by mass or less, more preferably 0.8% by mass or less, especially 0.7% by mass or less, suitable It is used as a lubricating oil composition for an internal combustion engine of a diesel vehicle equipped with a DPF.

When the lubricating oil composition for an internal combustion engine of the present invention has the above constitution, it becomes a lubricating oil composition for an internal combustion engine excellent in oxidation stability, base number maintenance, high-temperature detergency, and wear resistance of the valve system. Used as lubricating oil for internal combustion engines such as gasoline engines, diesel engines, and gas engines for motorcycles, automobiles, power generation, ships, etc., when it is finally substantially phosphorus-free, sulfur-free, and metal-derived sulfated ash content is 0.7% by mass or less , it is particularly suitable for use in internal combustion engines equipped with exhaust gas aftertreatment devices.

It is particularly preferable to be able to use low-sulfur fuels such as gasoline, light oil, kerosene, LPG, natural gas, or substantially no sulfur content, with a sulfur content of 50 mass ppm or less, more preferably 30 mass ppm or less, particularly preferably 10 mass ppm or less. Lubricating oil for internal combustion engines, especially for gasoline engines or gas engines, for fuels (hydrogen, dimethyl ether, ethanol, GTL (gas-to-liquid) fuel, etc.).

It can also be suitable as lubricating oil, lubricating oil, lubricating grease, wet brake oil, hydraulic oil, turbine oil, compressor oil, etc. , bearing oil, refrigerating machine oil and other lubricating oil to use.

[Example]

The content of the present invention will be described more specifically below by way of examples and comparative examples, but the present invention is not limited to these examples.

(A) Comparison of basic performance

<1. Evaluation test method>

As shown in Table 1, the lubricating oil composition for internal combustion engines of the present invention (Example 1) and the lubricating oil composition for internal combustion engines for comparison (Comparative Example 1) were prepared, respectively.

Table 1 Example 1 Comparative example 1 Cooperate Lubricant base oil ^* 1) mass% margin margin (A) Boric acid ester ^* 2) Mass % Boric acid element conversion amount mass % 1(0.05) -- (B) Ashless antioxidant ^* 3) % by mass 1 1 (C) Metal-based detergents ^* 4) Mass % in terms of metal elements mass % 3.3(0.2) 3.3(0.2) (D) Ashless dispersant ^* 5) Mass% Nitrogen equivalent mass% 5(0.075) 5(0.075) Dithiophosphate Metal Salt ^* 6) Mass% Phosphorus Conversion Mass % Sulfur Conversion Mass % --- 1.25(0.09)(0.2) Viscosity index improver ^* 7) mass% 4 4 Anti-emulsifier ^* 8) mass% 0.01 0.01 Element Phosphorus content of the composition mass % total sulfur content of the composition mass % sulfated ash derived from metal mass % 0.000＜0.010.67 0.090.20.83 performance test Heat pipe test (best: 10) 300°C 310°C 320°C 1097 640 Residual base value after ISOT test (HCl method) 48 hours % Temperature: 165.5 ° C 96 hours % 7464 4634 Base value residual rate after NOx absorption test (HCl method) 10 hours % Temperature: 150°C 20 hours % 6439 5318 Valve system wear test (JASO M328-95) Rocker pad scratch area % Rocker wear μm Cam wear μm 5.11.62.1 15.81.45.3

^* 1) Hydrotreated mineral oil, total aromatic content: 5.0% by mass, sulfur content: 0.001% by mass; kinematic viscosity at 100°C: 5.6mm ² /s; viscosity index: 125; NOACK evaporation: 8% by mass;

^* 2) tributyl borate, boron content: 4.8% by mass;

^* 3) A mixture of octyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate and alkyl diphenylamine (alkyl: C4 and C8) (mass ratio 1:1 );

^* 4) Calcium salicylate, metal ratio: 2.7, calcium content: 6.0% by mass, sulfuric acid ash: 20.4% by mass;

^* 5) Polybutenyl succinimide (double type), polybutenyl number average molecular weight: 1300, nitrogen content: 1.5% by mass;

^* 6) Zinc dialkyldithiophosphate, phosphorus content: 7.2% by mass, sulfur content: 15.2% by mass, zinc content: 7.8% by mass, alkyl group: 1,3-dimethylbutyl, sulfuric acid ash content: 11.7 quality%;

^* 7) The average molecular weight of OCP is 150,000;

^* 8) Polyalkylene glycol-based.

The ingredients used when compounding each composition are roughly as follows.

(base oil)

Hydrorefined mineral oil was used. The mineral oil had a total aromatic content of 5.0% by mass and a sulfur content of 0.001% by mass. In addition, the kinematic viscosity at 100° C. was 5.6 mm ² /s, the viscosity index was 125, and the NOACK evaporation amount was 8% by mass.

((A) Borate)

In the composition of Example 1 tributyl borate was used. The boron content was 4.8% by mass.

((B) Ashless Antioxidant)

Mix octyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate and alkyl diphenylamine (alkyl: C4 and C8) in a mass ratio of 1:1 use.

(metal dithiophosphate)

Zinc dialkyldithiophosphates are used. Zinc dialkyldithiophosphate having a phosphorus content of 7.2% by mass, a sulfur content of 15.2% by mass, and a zinc content of 7.8% by mass was used. The alkyl group was 1,3-dimethylbutyl, and the sulfated ash content was 11.7% by mass.

((C) Metal-based detergent)

Calcium salicylate (sulfur-free) was used. The metal ratio was 2.7, the calcium content was 6.0% by mass, and the sulfated ash content was 20.4% by mass.

((D) Ashless Dispersant)

Polybutenyl succinimide (double type) was used. The number average molecular weight of the polybutene group was 1300, and the nitrogen content was 1.5% by mass.

(viscosity index improver and demulsifier)

An olefin copolymer (OCP) was used as a viscosity index improver, and a polyalkylene glycol-based substance was used as an anti-emulsifier.

The performance evaluation of each obtained composition was performed by the following test.

(1) High temperature detergency seen in the heat pipe test

The heat pipe test was carried out according to JPI-5S-5599 standard. The score was colorless and transparent (no pollution) as 10 points, and black opaque as 0 points, and the evaluation was performed with reference to a standard tube prepared in advance with a scale of 1 in between. The results of this evaluation are shown in Table 1. If the score is 6 or higher at 290°C, the detergency is excellent as a lubricating oil for ordinary gasoline engines and diesel engines, and as a lubricating oil for gas engines, it is above 300°C in this test It also has excellent detergency, for example, a score of 8 or higher at 300°C, a score of 5 or higher at 310°C, and a score of 2 or higher at 320°C are all preferable.

(2) Changes in total base number over time measured by ISOT (Oxidation Stability of Lubricating Oils for Internal Combustion Engines; Indiana Oxidation Test)

According to the ISOT test (temperature: 165.5°C, air blowing rate: 10L/Hr, catalyst: copper, iron) of 4. in JIS K 2514 "Lubricating Oil - Oxidation Stability Test Method", the test oil was forced Time-dependent changes in the residual ratio of the total base number (hydrochloric acid method) at the time of deterioration. The results are shown in Table 1. The higher the total base number residual rate relative to the test time, the higher the base number maintenance, and it is shown that it is a long-lasting oil that can be used for a longer period of time.

(3) The change of total base number measured by NOx absorption test over time

Blow NOx gas into the test oil under the conditions in accordance with the 1992, 10, 465 standard (150°C, NOx: 1198ppm) of the Japanese General Lubrication Technology Conference Preliminary Collection to perform forced deterioration, and measure the total base number at this time (hydrochloric acid method) changes over time. The evaluation results are shown in Table 1. The higher the total base number residual ratio relative to the test time, the higher the base number maintenance even in the presence of NOx as used in internal combustion engines, indicating that it is a long-lasting oil with a longer service life.

(4) Wear test of valve system

According to JASO (Japan Automobile Technicians Association Standard) M 328-95, the valve wear test was carried out, and the scratch area (%), rocker arm wear (μm) and cam wear (μm) after 100 hours were measured. ). If the respective values are 10 or less, it means that the compositions are extremely excellent in valve system wear resistance. In this test, gasoline with a sulfur content of 10 mass ppm or less was used as fuel.

<2. Evaluation test results>

As shown in Table 1, it can be seen that the long-term oil with excellent oxidation stability, base number maintenance, high temperature detergency and anti-wear performance is an internal combustion engine containing ordinary zinc dialkyldithiophosphate. Compared with the lubricating oil composition (Comparative Example 1), the lubricating oil composition for an internal combustion engine of the present invention (Example 1) exhibited extremely excellent oxidation stability, base number maintenance at high temperature and in the presence of NOx, and High-temperature detergency, and the anti-wear performance of the valve system is not inferior.

(B) Changes in properties of the valve system before and after the wear test

The total acid value increase rate and viscosity of the compositions of Example 1 and Comparative Example 1 were measured for the test oil before and after the valve wear test using gasoline having a sulfur content of 10 mass ppm or less in the above-mentioned Example A (4). The rate of increase and the residual rate of total base number were compared. As a result, it was confirmed that, compared with the composition of Comparative Example 1, the composition of Example 1 suppressed both the total acid value increase rate and the viscosity increase rate relatively low, and the total base number residual rate was increased.

(C) Influence of the metal ratio of the metal-based detergent on the performance of the composition

The metal ratio of calcium salicylate in Example 1 and Comparative Example 1 was changed, and the calcium salicylate was changed to calcium sulfonate, and the above-mentioned heat pipe test, ISOT test and NOx absorption test were performed to evaluate oxidation stability and base number. Maintenance and high temperature detergency. The content of the metal-based detergent in the composition was prepared in the same amount in terms of metal elements.

(1) Composition C1 using calcium salicylate having a metal ratio of 3 or more, specifically, calcium salicylate having a metal ratio of 4.3 instead of calcium salicylate having a metal ratio of 2.7 in the composition of Example 1 was prepared. Moreover, the composition C2 which used the calcium salicylate whose metal ratio was 4.3 instead of the calcium salicylate which was 2.7 in the composition of the comparative example 1 was prepared. Composition C1 exhibits better oxidation stability, base number maintenance, and high-temperature detergency than composition C2. However, the composition of Example 1 showed more excellent performance than composition C1.

(2) On the other hand, after using calcium salicylate with a metal ratio of 1.5 or less, specifically, calcium salicylate with a metal ratio of 1, or using both a salicylate with a metal ratio of 1.5 or less and a salicylate with a metal ratio of 2.7 Compositions C3 and C4 were prepared by replacing calcium salicylate having a metal ratio of 2.7 in the composition of Example 1 with calcium salicylate having a ratio of 1.8 to 2.3, specifically 2.1. In the case of compositions C3 and C4, compared with the composition of Example 1, the oxidation stability, base number maintenance, and high-temperature detergency were shown to be more excellent.

(3) Composition C5 was prepared by using calcium sulfonate (sulfur-containing metal-based detergent) having a metal ratio of 10 instead of calcium salicylate having a metal ratio of 2.7 blended in the composition of Example 1. Composition C6 was prepared by using calcium sulfonate (sulfur-containing metal-based detergent) having a metal ratio of 10 instead of calcium salicylate having a metal ratio of 2.7 blended in the composition of Comparative Example 1. Composition C5 showed more excellent oxidation stability, base number maintenance and high-temperature detergency than composition C6, but compared with the composition of Example 1, the base number residual rate was worse. However, when the composition C7 was prepared with a metal ratio of 1.5 or less, for example, calcium salicylate having a metal ratio of 1 as an essential component, and simultaneously using calcium sulfonate having a metal ratio of 10, compared with composition C5, Base number maintenance, especially in the presence of NOx, is greatly improved.

Industrial availability

The lubricating oil composition for an internal combustion engine of the present invention, because it does not contain phosphorus substantially and is low in sulfur, can exhibit excellent performance in terms of valve system wear resistance, oxidation stability, high temperature detergency, and alkali number maintenance. Therefore, it can be preferably used as a lubricating oil for internal combustion engines such as gasoline engines, diesel engines, and gas engines for motorcycles, automobiles, power generation, and ships, and is particularly suitable for use in internal combustion engines equipped with exhaust gas after-treatment devices.

In addition, it is preferable to be able to burn low-sulfur fuels such as gasoline, light oil, kerosene, LPG, natural gas or substantially no sulfur fuel (hydrogen, dimethyl ether, ethanol, GTL (gas-to-liquid) with a sulfur content of 50 mass ppm or less. ) fuel, etc.) lubricating oil for internal combustion engines, especially gasoline engine or gas engine lubricating oil is used.

Not only as lubricating oil for internal combustion engines, but also suitable as lubricating oils that require such performance, such as lubricating oils for driving systems such as automatic or manual transmissions, grease, wet brake oil, hydraulic oil, turbine oil, compressor oil, bearings Oil, refrigeration oil and other lubricating oil to use.

Claims (10)

1. A lubricating oil composition for an internal combustion engine, characterized in that: in the lubricating oil base oil composed of mineral oil and/or synthetic oil, based on the total amount of the composition, it contains 0.001～ 0.5% by mass of (A) borate ester and 0.01 to 5% by mass of (B) ashless antioxidant, substantially no metal dithiophosphate, and the sulfur content of the composition is 0.2% by mass or less. 2. The lubricating oil composition for an internal combustion engine according to claim 1, wherein the total aromatic content of the lubricating base oil is adjusted to be 10% by mass or less, and the sulfur content is adjusted to be 0.05% by mass or less . 3. The lubricating oil composition for an internal combustion engine according to claim 1 or 2, characterized in that it contains (C) a metal-based detergent in an amount of 0.005 to 1% by mass in terms of metal elements based on the total amount of the composition . 4. The lubricating oil composition for an internal combustion engine according to claim 3, wherein the metal ratio of the component (C) is 3 or less. 5. The lubricating oil composition for an internal combustion engine according to claim 3 or 4, wherein the component (C) is a sulfur-free metal-based detergent. 6. The lubricating oil composition for an internal combustion engine according to any one of claims 1 to 5, characterized in that it contains (D) in an amount of 0.05 to 0.4% by mass in terms of nitrogen element based on the total amount of the composition. Ashless dispersant. 7. The lubricating oil composition for an internal combustion engine according to any one of claims 1 to 6, characterized in that it does not substantially contain phosphorus and has a total sulfur content of 0.05% by mass or less. 8. The lubricating oil composition for an internal combustion engine according to any one of claims 1 to 7, which is used in an internal combustion engine using a fuel having a sulfur content of 50 mass ppm or less. 9. A lubricating method for a valve mechanism of an internal combustion engine, characterized in that: using the following lubricating oil composition, the lubricating oil composition is, in a lubricating oil base oil composed of mineral oil and/or synthetic oil, with Based on the total amount of the composition, it contains 0.001 to 0.5% by mass of (A) borate ester and 0.01 to 5% by mass of (B) ashless antioxidant in terms of boron element conversion, and does not substantially contain dithiophosphoric acid As for the metal salt, the sulfur content of the composition is 0.2% by mass or less. 10. A long-acting method for a lubricating oil composition for internal combustion engines, characterized in that: in the lubricating oil base oil composed of mineral oil and/or synthetic oil, based on the total amount of the composition, it contains The amount is 0.001 to 0.5% by mass of (A) boric acid ester and 0.01 to 5% by mass of (B) ashless antioxidant, substantially does not contain dithiophosphate metal salt, and the sulfur content of the composition is 0.2% by mass the following.